SUMMARY (Revisions in blue font) Effective treatment of high-impact pain patients is one of the major stated goals of the National Pain Strategy. Identification of new targets and mechanisms underlying neuropathic pain will be critical in developing new target-specific medications for better neuropathic pain management. We recently discovered that peripheral nerve injury-induced upregulation of an axonal guidance phosphoprotein collapsin response mediator protein 2 (CRMP2) and the N-type voltage-gated calcium (CaV2.2) as well as the NaV1.7 voltage-gated sodium channel, correlates with the development of neuropathic pain through an unidentified mechanism. In our preliminary studies, we found that interfering with the phosphorylation status of CRMP2 is sufficient to confer protection from chronic pain. Others have found that a CRMP2 knock-in mutant mouse where the phosphorylation site Ser522 was inactivated with alanine (crmp2S522A) had a decreased sensitivity to pain. A mechanistic link between prevention of CRMP2 phosphorylation and effects on dysregulated excitatory synaptic transmission underlying neuropathic pain processing has never been investigated. Whether there is a phosphoregulatory ?set-point? permitting CRMP2 to ?toggle? between a presumptive non-phosphorylated (non-pain) and phosphorylated (pain) state is not known. We find that the ratio of pCRMP2:CRMP2 varies in human spinal cords. Based on the literature and our preliminary data, we hypothesize that injury induced phosphorylated-CRMP2/CaV2.2 and phosphorylated-CRMP2/NaV1.7 upregulation in the sensory pathway promotes abnormal excitatory synaptic transmission in spinal cord that leads to neuropathic pain states. In Aim 1, we will determine the molecular/cellular mechanisms underlying aberrant excitatory synaptic transmission and neuropathic pain processing in conditions wherein CRMP2 phosphorylation is inhibited. In Aim 2, we will attempt to directly tackle NIH?s Helping to End Addiction Long-term (HEAL) initiative to speed scientific solutions to the national opioid public health crisis by: (a) determining the side-effect profile and abuse liability of targeting CRMP2 phosphorylation with a small molecule, and (b) determine if CRMP2 with a small molecule can be opioid sparing or decrease opioid abuse liability. We propose to validate CRMP2 phosphorylation as a novel target in neuropathic pain using innovative tools that include a genetic approach (crmp2S522A) mice as well as a non-opioid pharmacological approach (a novel CRMP2-phsphorylation targeting compound). The expected results of this application are translationally significant in that they will establish CRMP2-phosphorylation as a novel pain therapeutic target. By demonstrating that inhibition of CRMP2 phosphorylation reverses or prevents neuropathic pain, we will promote the discovery and validation of a novel therapeutic target (CRMP2-phosphorylation) to facilitate the development of novel pain therapeutics ? thus directly addressing the mandate of RFA-NS-18-043.